1. Field of the Invention
The present invention relates to read-write apparatus and methods for reading and writing information on a recording media using a read-write head which contacts the recording media.
2. Description of the Related Art
As an example of the read-write apparatus of a prior art, a magnetic disk apparatus is explained. In the magnetic disk apparatus of the prior art, the read-write head ("head" hereafter) consisting of a head slider of magnetic head flies above the surface of the recording media ( "disk" hereafter) using pressure generated by air while the disk rotates at high speed. The information is read and written under a condition that spacing between the head and the disk is almost fixed. In short, the head does not contact the disk while the diak is rotating. The head does not slide on the disk.
However, when recording wave length becomes short to improve recording-density, if the spacing between the head and the disk is kept constant, output from the magnetic head decreases. Therefore, it is necessary that flying height of the head become smaller. However, there are limits on how small the flying height can be. Recently, a magnetic disk apparatus which contacts the recording surface has been developed.
In the magnetic disk apparatus with contact recording heads, the head always contacts the disk and slides on the disk. Therefore, it often happens that both surfaces of the head and the disk are worn. In order to decrease wear of the head and the disk, the load force of the head to the disk should be decreased as much as possible (as disclosed in Japanese Patent Disclosure (Kokai) No.7-307069). However, the wear of the head and the disk is not entirely avoided. As for the wear of the head, structure not have influencing magnetic function is prepared in the magnetic disk even if the head is worn to some extent. Under this structure, some wear is permissible (as disclosed in "H. Hamilton, IEEE Trans. on Magn., Vol.27, No.6-pp 4921-4926 (1991)).
On the other hand, as for the wear of the disk, the disk is fatally wounded if the magnetic layer of the disk is greatly worn. Therefore, the wear of the disk should be avoided to the utmost. However, if the head is frequently located on a specific area (e.g. the area to store information to control file) wear progresses move quickly on the specified area.
As mentioned above, in a read-write apparatus which contacts the recording, if the head slides on the specified area of the disk at excessive times, the wear progresses on that specific area.